Process for producing masonry block with roughened surface

ABSTRACT

A mold box for producing a plurality of masonry units with a roughened texture side face, the mold box including a plurality of side walls defining a mold cavity open at its top and bottom, adapted to receive masonry fill material by way of its open top, and to discharge molded fill material in the form of a molded masonry unit of predetermined height by way of its open bottom; and a division member spanning between two of the side walls to define two subcavities in the mold box, the division member comprising a grate.

BACKGROUND OF THE INVENTION

[0001] The typical automated process for making a masonry unit comprisesthe steps of placing a mold which is open at the top and bottom on asolid pallet, filling the mold with a suitable composite material(generally comprising cement and aggregate material), vibrating thefilled mold and/or the pallet while simultaneously compacting thematerial within the mold via a compression head inserted into the top ofthe mold to density the composite material, stripping the moldedcomposite material (still resting on the pallet) from the mold, andcuring the molded composite material to form a masonry unit.

[0002] It is now also common to split off a portion of the cured masonryunit so as to create a decorative face on the unit. The splittingprocess creates an irregular texture, and exposes, and may actuallybreak, some of the aggregate material in the composite. The face createdby the splitting process is often referred to in the industry as “splitface”, or “rock face”.

[0003] The splitting of cured masonry units by this process involvesadditional equipment and manufacturing steps. In order to avoid theadded costs associated with the splitting process, there have beenefforts to alter the configuration of the mold so as to achieve the same“split face” texture on the masonry unit without the additionalsplitting steps.

[0004] For example, U.S. Pat. No. 3,981,953 describes a mold in which aplurality of patterning elements are suspended in a frame in ahorizontal array below and parallel to the compression head of themolding machine. These elements are positioned to correspond with adesired pattern of lines on the finished product. A plurality of smallerrods, arrayed at right angles to the patterning elements may also bemounted in the frame. After the mold box is filled, the compression headis lowered into the mold box, thus burying the patterning elements inthe composite material. Upon stripping of the mold, retraction of thecompression head pulls off the top layer of composite material, which isheld between the head and the patterning elements. The result is thatthe pattern of the array of elements is impressed on the top of themasonry unit. Between the marks left by the patterning elements, aroughened texture is produced. This arrangement produces a pattern onthe top face of the masonry unit, as molded.

[0005] There are a number of applications, however, when the face of theunit that must be textured is not the top face of the unit as molded,but, rather, is one of the vertical side faces of the unit. The '953patent describes a modification of the process, where the frame holdingthe array of patterning elements is inserted vertically into the moldalong and parallel to one side wall of the mold. The mold is filled andvibrated. When the molded masonry unit is stripped from the mold, it isstripped with the frame holding the array of patterning elements stillembedded in the molded unit. After stripping, the frame and array ofelements is pulled away from the vertical face of the molded unit in adirection normal to the face, pulling a portion of the molded unit awayat the same time to expose the pattern on the vertical side of themolded unit, with roughened areas between the pattern lines. Thus it isan extremely cumbersome and impractical process to achieve a roughenedtexture on a vertical side of the masonry unit as cast with the processof the '953 patent. And whether the treated surface is the top or sideof the masonry unit, the composite material has to be cleaned from thearray of patterning elements after each cycle of the machine.

[0006] U.S. Pat. No. 3,940,229 describes a process for achieving aroughened texture on the vertical side of a masonry unit as molded. Thepatent describes a mold in which a small lip is formed on the inner,lower edge of a vertical wall of the mold. As the densified, compositematerial is stripped from this mold, the lip moves vertically up theside wall of the masonry unit, and tears some of the composite materialaway from the main mass. The lip temporarily retains this compositematerial in place against a portion of the mold wall as the mold isstripped. The retained material is thus dragged, or rolled, up the faceof the main mass as the mold is stripped, creating a random, roughenedtexture on the vertical side face of the masonry unit. An improvement onthis process is described in U.S. patent application Ser. No.08/748,498, filed Nov. 8, 1996, which is assigned to the same assigneeas the present application.

[0007] The process of the '229 patent, and the improved process of the'498 application retain a small amount of material against the mold wallas the mold is stripped. These processes create a rough textured face ona concrete masonry unit, but the texture can have a “shingled”appearance.

[0008] Another example of an alternative to splitting is shown in U.S.Pat. Nos. 5,078,940 and 5,217,630. The molds described in these patentsmake use of a lower lip on a vertical wall of the mold, similar to thatshown in the '229 patent. In addition, the molds employ a plurality ofprojections on the associated vertical mold wall above the lip, and avertically oriented reinforcing mesh above the lip and inboard from thewall. This combination of reinforcing mesh and projections is similar tothe array of patterning elements and normally-oriented rods described inthe '953 patent. When the mold is initially filled, the compositematerial fills in between the mesh and the wall, and around theprojections. When the mold is vibrated, the material is compacted. Thecombination of lip, mesh and projections holds a large mass ofcompacted, composite material against the mold wall as the mold isstripped. These patents show the retained mass of composite materialshearing from the rest of the composite material, to create a roughenedface on the molded unit that is stripped from the mold.

[0009] In the process of the '940 and '630 patents, the use of theprojections (whether or not in combination with a reinforcing mesh)holds a much larger mass of material against the mold side wall than isthe case in the '229 process, and does so in such a fashion as to retainthat material in the mold from cycle to cycle. This creates what isperceived to be a potential drawback of the process of the '940 and '630patents: it is not self cleaning, and it can be difficult and/or timeconsuming to clear the retained material from the mold side wall, whichapparently need not be done on every machine cycle, but must be doneperiodically. On the plus side, this process can create a face whichdoes not evidence as much “shingling” as with the '229 process.

[0010] Accordingly, there is a need for a self-cleaning mold assemblywhich will produce a random, roughened texture face that does notevidence any “shingling” on a vertical side face of a masonry unitwithout a splitting step, so that the manufacturing process can operatewithout periodic cleaning or maintenance for extended production runs.

SUMMARY OF THE INVENTION

[0011] The invention is a self-cleaning mold assembly which will producea random, roughened texture face that does not evidence any “shingling”on a vertical side face of a masonry unit without a splitting step, sothat the manufacturing process can operate without periodic cleaning ormaintenance for extended production runs.

[0012] The mold comprises a standard masonry mold assembly including amold box which is open at the top and bottom, and a complementarycompression head/stripper shoe plate. The cavity defined by the mold boxis divided into at least two subcavities by a vertically-orienteddivision member comprising a grate. The compression head is shaped sothat it can move into, and through, each subcavity of the mold duringthe compaction and stripping operations. In operation, a metal pallet isplaced under the mold. The mold cavity is filled via its open top, withthe composite material filling in each mold subcavity. The compositematerial is densified in the mold by vibration of the mold, the pallet,or both. The compression head further compacts the composite, and thenmoves through the mold subcavities as the pallet is moved downwardlyaway from the mold, to strip all of the compacted material out of themold. The stroke of the machine thus produces at least two moldedmasonry units. The faces of the resulting units which were adjacent thegrate in the mold have a random, roughened texture, without shingling,that approximates the “split face” achieved by splitting cured masonryunits. Since the compression head moves down through the mold adjacenteach side of the grate, the mold is self-cleaning, and can be used inextended production runs without stopping for periodic cleaning ormaintenance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of a mold box in accordance with theinvention.

[0014]FIG. 2 is a sectional view of the mold box shown in FIG. 1 takenat line 2-2.

[0015]FIG. 3 is a view similar to that shown in FIG. 2 additionallyshowing the mold box filled with composite material and a sectional viewof the stripper shoe plate.

[0016]FIG. 4 is a view similar to that shown in FIG. 3 showing theaction of the stripper shoe plate as the densified composite material isstripped from the mold.

[0017]FIG. 5A is a perspective view of a block made with the process ofthe invention using the mold depicted in FIG. 1.

[0018]FIG. 5B is a perspective view of an alternative embodiment of ablock made in accordance with the process of the invention.

[0019]FIG. 6 is an enlarged view of the raised expanded metal gratingused in preferred form of the invention.

[0020]FIG. 7 is a perspective view of a mold in accordance the inventionadapted to make blocks of a different shape.

[0021]FIG. 8 is a perspective view of a division member for the moldshown in FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The invention is a self-cleaning mold for producing a pluralityof masonry units or blocks, each with a roughened texture side surface,without the use of apparatus such as splitters. The invention may beused with different types of molds to produce different types of blocks,such as decorative architectural blocks, paving stones, landscapingblocks, retaining wall blocks, etc. An example of the mold 10 isschematically shown in FIG. 1. The mold comprises a mold box made up ofside walls 16, 18, 20 and 22, and is open at its top and bottom. Themold is adapted to rest on a pallet 60 (FIG. 3), to receive compositematerial. The mold box comprises subcavities 12 and 13, separated bydivision member 14. Division member 14 comprises a grate 24 defined bysolid portions and open portions. In the preferred mold box, the grate24 is vertically oriented and spans from side wall to side wall and fromtop to bottom of the mold box.

[0023] A molded masonry unit will be produced by each subcavity of themold, and the preferred grate 24 configuration will produce a roughenedtexture on the entire face of each molded unit that contacts the grate24. If, however, it is not desirable to texture that entire face, thegrate 24 can be located in only a portion of the division member 14defining the subcavities, such as on one end, or in the central portionof that division member 14. The side walls of the mold will typically bemade up of a series of wear parts, which are not shown in FIG. 1, butwhich are well known to those of skill in the art. Also not shown arethe side bars, spill plate, and other associated parts that are commonin this type of mold, and which are also well known to those of skill inthe art.

[0024] The preferred configuration of the material from which the grateis constructed is shown in more detail in FIG. 6. The preferred gratecomprises a panel of raised expanded metal grating. It is believed thatthe process for making the grate 24 comprises slitting and stretchingsolid sheets or plates of metal. The preferred grate 24 comprises aplurality of strands 23 configured in a diamond pattern with openings25. The strands 23 are somewhat twisted and offset as a result of theexpanded metal manufacturing process. Referring to FIG. 6, thedimensions (in inches) of the preferred grate are: Diamond Size (SWD ×LWD) 1.41 × 4.00 Opening Size (SWO × LWO) 1.00 × 2.88 Strand Size (width× thickness) .300 × .250 Depth 5/8 Percent Open Area 58 Lbs. per squarefoot  4.27

[0025] Expanded metal grating is commercially available from EXMETIndustries Inc. in the size described, and in a variety of otherdimensions, as well. The SWD of expanded metal grating available fromEXMET varies from about 1.33 to 2.00 inches. The LWD varies from about4.00 to 6.00. The SWO varies from about 0.813 to 1.625. The LWO variesfrom about 3.4 to 4.88. The strand 23 width varies from about 0.215 to0.410. The strand 23 thickness varies from about 0.183 to 0.312. Thedepth varies from about {fraction (9/16)} to about ¾. The percent openarea varies from about 45 to 69%. The weight per square foot varies fromabout 3 to 7 pounds. All of these standard expanded metal gratings couldbe used in the present invention. It is also believed that expandedmetal panels in lighter and heavier gauges and in different patternsthan those used for grating can also be used, so long as the material issufficiently durable for the presented environment. It is also possibleto combine two expanded metal panels back to back to create the grate.It is also possible to combine an expanded metal panel with a solidpanel, so that the roughened texture will be produced on only one faceof a molded unit in one subcavity of the mold box.

[0026] The material of the preferred grate is carbon steel, but avariety of materials could be used, so long as they produce a durablegrate suitable for the presented environment.

[0027] It is also believed that the grate could be formed by a varietyof processes other than that used to produce expanded metal, such as bypunching or drilling openings in a metal sheet, cutting openings in ametal sheet with a torch, twisting or welding individual strandstogether, etc.

[0028] The grate must be mounted in a manner that provides durability inthe presented environment, as well. In the presently preferredembodiment, the grate 24 is simply welded to the side walls of the moldbox. It could, however, be affixed to support elements (33 and 35, FIG.8) which, in turn, are affixed to the side walls of the mold box bywelding, bolting, or other suitable means.

[0029] The mold box works in conjunction with a stripper shoe head. Asshown in FIGS. 2 through 4, the stripper shoe head 40 comprises strippershoe plates (40 a and 40 b), each of which is associated with asubcavity of the mold box 10. Each stripper shoe plate conforms in shapeand size with the top plan shape and size of the subcavity with which itis associated. The stripper shoe plates is preferably sized so as toprovide about {fraction (1/16)} inch of clearance with the mold sidewalls and the grate 24. This clearance allows the plates 40 a and 40 bto move downwardly through the mold box 10 as the mold is stripped, butdoes not permit composite material to move upward past the plate edgesduring stripping (which would create “feathered” edges on the moldedproduct).

[0030] To use the invention, a pallet 60 is moved into place beneath themold 10, as shown in FIG. 3. The pallet 60 may be made of wood, plastic,or metal. The mold is then loaded with composite masonry fill 50 throughits open top to a predetermined initial fill level 62. Composite masonryfill generally is composed of aggregate material, cement, and water. Itmay include other ingredients, such as pigments, plasticizers, and otherfiller materials, depending upon the particular application.

[0031] The mold 10, or pallet 60, or a combination of both, may bevibrated for a suitable period of time to assist in the loading of themold 10. The stripper shoe plates 40 a and 40 b are then moved into themold box 10 to bear on the fill 50. Additional vibration, in concertwith pressure exerted through the plates acts to densify the compositefill to the desired density and to achieve the predetermined, finalheight of the molded unit. Once this is achieved, relative movement ofthe stripper shoe plates 40 a and 40 b and the pallet 60 with respect tothe mold box 10 strips the molded unit from the mold box (FIG. 4). Themold filling time, the vibration times and the amount of pressureexerted by the plates are determined by the particular machine used, andthe particular application. For a Besser V3 12 block machine, typicalsettings for this application would be: 1¾ seconds feed time, withvibration on; a ⅛ inch spring gap setting to establish the pressureexerted by the plates; and a 2 second finish time with plate pressureand vibration exerted on the fill mass.

[0032] The action of stripping the block from the mold 10 creates aroughened texture on those surfaces 45 of the fill mass that pass andcontact the grate 24 (see FIGS. 5A and 5B). Thus, with the mold shown,two molded units, each having a roughened face 45, are produced witheach cycle of the machine. These units are subsequently transported to asuitable curing station, where they are cured with suitable techniquesknown to those of skill in the art. Curing mechanisms such as simple aircuring, autoclaving, steam curing or mist curing are all useful methodsof curing the block resulting from the invention.

[0033] It is preferred that each subcavity of the mold be ofsubstantially the same shape and size, so that all of the molded unitsare substantially identical. It is possible, however to createsubcavities that are not substantially identical, thereby producingmolded units of different shapes or sizes with each cycle of themachine. It is also possible that not all of the molded units producedwill be passed to the curing station. For example, one of the moldedunits may be reclaimed, and recycled as fill material, rather thancured.

[0034] Blocks of shapes other than rectangular may be made with thepresent invention. For example, the mold shown in FIG. 7 may be used toproduce a block of a different shape. The mold box 10 comprises sidewalls 16, 18, 20, 22, and 26, and includes subcavities 12 and 13separated by division member 14, and subcavities 12′ and 13′, separatedby division member 14′. The division members comprise a grate 24 and24′.

[0035] The mold side walls include wedge walls 15, 17, 19, and 21 toform features on the molded units. Lower lips 32 are formed on each ofthese wedge walls. Preferably, the lower lips extend from the wedgewalls 15 and 17 into the cavity approximately 0.187 inches. The shape oflower lips 32 in cross section is preferably a wedge. The presentlypreferred dimensions of the lip are a thickness of about ¼ inch adjacentwalls 15 and 17, and a thickness of about {fraction (1/16)} inch at isoutboard end. The presently preferred profile of the lower lip is thatit be a straight outboard edge long its entire length. However, othershapes, such as a serrated edge or a scalloped edge, can be used toproduce different roughened textures on the face of the finished masonryunit.

[0036] The lower lips 32 may be releasably attached to the side wall bymeans such as bolts, screws, etc. which allows for their removal. Thisis important because the lower lips 32 are wear points in the moldapparatus and may after time tear, chip or break. Alternatively, thelower lip 32 may be welded to the wedge walls, or formed integrallytherewith. The wedge walls 33 and 35 and grate panel 24 can beincorporated into a division member 14, as shown in FIG. 8. In thiscase, the grate 24 is welded to the wedge pieces, which, in turn areadapted to be bolted 39 into the mold box side walls. Upper lips 34assist in forming the roughened surfaces of molded units made inaccordance with the invention. These upper lips can be seen in U.S.patent application Ser. No. 08/748,498 filed Nov. 8, 1996 which isincorporated herein by reference.

[0037] The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

The claimed invention is:
 1. A mold box for producing a masonry unitwith a roughened texture side surface comprising: a) a plurality of sidewalls defining a mold cavity open at its top and bottom, adapted toreceive masonry fill material by way of its open top, and to dischargemolded fill material in the form of a molded masonry unit ofpredetermined height by way of its open bottom; and b) a division memberlocated between two of said side walls to define two subcavities in themold box; c) said division member comprising, at least in part, a grate.2. The mold box of claim 1 wherein said division member is orientedsubstantially vertically.
 3. The mold box of claim 2 wherein said grateextends substantially from side wall to side wall, and from the top tothe bottom of the mold cavity.
 4. The mold box of claim 3, wherein saidgrate is affixed directly to said side walls.
 5. The mold box of claim3, wherein said grate is affixed to first and second end supports,which, in turn, are affixed to the side walls.
 6. The mold of claim 5,wherein said first and second supports are bolted to said side walls. 7.The mold box of claim 1 wherein the grate comprises a panel of expandedmetal.
 8. The mold box of claim 7 wherein the panel comprises raisedexpanded metal.
 9. The mold box of claim 8 wherein the panel comprisesraised expanded metal grating.
 10. The mold box of claim 9 wherein theopenings in the expanded metal grating have a dimension in the SWdirection in the range of about 0.813 inch to about 1.625 inches, and inthe LW direction in the range of about 2.88 inches to about 4.88 inches.11. The mold box of claim 1 wherein the grate comprises two panels ofraised expanded metal.
 12. The mold box of claim 1 wherein there iscommunication between the subcavities of the mold box via openings inthe grate.
 13. The mold box of claim 1, wherein said subcavities are ofsubstantially equal shape and size.
 14. The mold box of claim 1, whereinthe side walls comprise a plurality of wear parts.
 15. The mold box ofclaim 1, wherein the grate comprises a panel of sheet metal with holespunched therein.
 16. A method of manufacturing masonry units with aroughened texture side surface, said method comprising the steps of: a)filling a mold box with composite masonry fill to a first level, saidmold box comprising a plurality of side walls defining a mold cavityopen at its top and bottom, adapted to receive composite masonry fillmaterial by way of its open top, and to discharge molded fill materialin the form of a plurality of molded masonry units of predeterminedheight by way of its open bottom, and division member spanning betweentwo of said side walls to define two subcavities, said division membercomprising a grate; b) compacting the masonry fill within the mold boxto a second level corresponding with the predetermined height of themolded masonry unit; c) discharging the molded masonry units from themold box, at least partially through the action of stripper shoe platesassociated with each subcavity of the mold box; and c) curing at leastsome of the discharged masonry units.
 17. The method of claim 16 whereinthe grate comprises a panel of raised expanded metal grating.
 18. Themethod of claim 17, wherein the subcavities are substantially equal inshape and size.
 19. The method of claim 16, wherein at least one of theside walls includes a lower lip adapted to texture the correspondingface of a molded masonry unit.
 20. The method of claim 16, wherein atleast some of the discharged masonry units are recycled as fillmaterial, rather than being cured.
 21. A masonry unit with a roughenedsurface resulting from the method of claim
 16. 22. A mold assembly forproducing a plurality of masonry units, each with a roughened textureside surface, comprising: a) a mold box comprising a plurality of sidewalls defining a mold cavity open at its top and bottom, said mold boxbeing adapted to rest on a pallet, and adapted to receive masonry fillmaterial by way of its open top, and to discharge molded fill materialin the form of a plurality of molded masonry units of predeterminedheight by way of its open bottom; b) a division member spanning betweenat two of said side walls to define two subcavities of the mold box, andcomprising a grate; and c) a stripper shoe plate associated with each ofthe subcavities.
 23. The mold assembly of claim 22, wherein thesubcavities are substantially the same size and shape.
 24. The moldassembly of claim 22, wherein the grate comprises a panel of raisedexpanded metal grating.
 25. The mold assembly of claim 24, wherein eachstripper shoe plate is sized to move through its associated subcavitywithout producing substantial feathering of the top edges of theresulting molded masonry unit.
 26. The mold assembly of claim 25,wherein the clearance between each stripper shoe plate and the sidewalls and the division member of its associated subcavity is about{fraction (1/16)} inch.
 27. A mold box for producing a plurality ofmolded masonry units, each having a roughened texture side face,comprising: a) a plurality of side walls defining a cavity open at itstop and bottom; b) a generally vertically oriented division memberspanning between two opposed side walls to define two subcavities, saiddivision member comprising a panel of raised expanded metal grating.